1. Field of the Invention
This invention relates to a process for forming dyed braided sutures.
2. Description of Related Art
Braided sutures are well known in the art as disclosed, for example in U.S. Pat. No. 5,019,093. Various natural and artificial polymeric materials have been used in manufacture of braided sutures, including surgical gut, silk, cotton, polyolefins, polyamides, polyglycolic acid and polyesters. Braided sutures are useful in applications where a strong, nonabsorbable suture is needed to permanently repair tissue. They are frequently used in cardiovascular surgery, as well as in ophthalmic and neurological procedures.
For various reason it is desirable to provide sutures which are dyed. For example, dyed sutures allow immediate suture brand and/or type recognition by the surgical team or treating physician as well as enhancing visibility of the suture in the surgical field. Previously, braided sutures were formed from braided yarns of thermoplastic, non-absorbable polymer which were textile dyed. The braided yarns had a reduced tenacity because it was easier to dye a less crystalline matrix. Thereafter, the dyed braids were stretched to increase their tenacity and to make the yarn more crystalline. However, braided yarns are not dyed thoroughly by conventional solution dyeing techniques even at such a lower tenacity. The braided yarns tended to resist uniform penetration by dye solutions. In particular, this is true of polyethylene terepthalate non-absorbable sutures.
More recently, higher molecular weight polyester fibers formed from polyethylene terephthalate have been employed as suture material. Such fibers have a relatively high initial tenacity and a relatively high intrinsic viscosity. It has proven necessary to dye such fibers by boiling the fibers in a dye solution. Even then, there is relatively low penetration of dye into the fibers. To obtain thorough dye uptake by the polyester fibers it has usually proven necessary to apply the dye solution at conditions of high pressure and high temperature. At such elevated pressures and temperatures, however, both the dye and fiber can be degraded.
Accordingly, it is desired to provide a method for incorporating dye uniformly into a suture material free of the defects and deficiencies of the prior art.